I couldnt agree with you more. I have been using this site for a couple of years now, and, have come across many many threads regarding tang/tank sizes. Now, im not saying its great to keep a tang in a 40g breeder, i think there are a lot of people out there who try to lay down the tang law without opening their eyes. Its all good and well to say 'no, no, no, that yellow tang simply must be in a 90g+ tank'. But some times its not quiet as simple as that. You could have a 200g tank with 500lbs of LR in it, will the fish have any more swimming room than if it were in a 55? probably not. I also think that there are far to many hobby newcomers with very little experience who try to grill people about tangs, is this too get a +1 and feel like a pro? i really dont know sometimes! Then on the other end of the scale there are advanced aquarists who have probably been reefing for 10 years + who think that just because your experienced enough to control amazing parameters with a huge bio-load in a small tank, its okay to do so. What amazes me about this the most is, the 'self proclaimed tang police praise them for it'! A recent example of this could be October's TOTM. Here we have an unquestionably beautiful SPS tank, packed to the rafters with LR, which holds a total volume of 80g of water. Fish list consisting of: A hippo TANG, and powder blue TANG, a regal angel, 3 two spot basslets, 9 red fin anthias, 10 chromis, a fairy wrasse, along with a few goby's. Now in the TOTM threat for that month im pretty sure i saw one or two of them shaking his hand?? Now im not saying that its right or wrong, just trying to get a point across. Its not always black and white. While tank size is important (I cry inside when i see some of these youtube clips with multiple fish in smaller systems) many other factors are also involved.
Just my 2c.